The present invention relates to a scanning electron microscope (SEM) capable of imaging a desired evaluation point on a sample and automatically measuring a desired dimension of a circuit pattern formed at the evaluation point, and to a measuring method therefor. Specifically, the present invention relates to an SEM device provided with an automatic recipe creating function of obtaining an SEM image of the desired evaluation point and automatically determining a recipe making it possible to perform a desired measurement (e.g., a measurement of wiring width of the line pattern or a measurement of a gap between the line patterns) at the evaluation point based on the design data of the circuit pattern without using a real wafer, and to a measuring method therefor. In the recipe, there are designated an imaging method of the SEM image of the evaluation point, a position and a shape of a dimension measurement cursor for measuring the dimension in the desired circuit pattern after taking the SEM image, and a dimension measurement method.
When forming a wiring pattern on a semiconductor wafer, there is adopted a method in which a coating material called resist is applied on the semiconductor wafer, an exposure mask (a reticle) for the wiring pattern is stacked on the resist, a visible light beam, an ultraviolet ray, or an electron beam is applied on the exposure mask, thereby exposing the resist to be developed, thus forming the wiring pattern with the resist on the semiconductor wafer, and then an etching treatment is executed on the semiconductor wafer using the wiring pattern, which is made of the resist, as a mask, thereby forming the wiring pattern. Since the wiring pattern made of the resist varies in the form of the pattern depending on the intensity and aperture of the visible light beam, the ultraviolet ray, of the electron beam applied to the wiring pattern, it is necessary to examine the facture of the pattern in order to form a highly accurate wiring pattern. In the examination described above, critical dimension scanning electron microscopes (CD-SEM) have been used widely in the past.
The coordinate point, at which the SEM imaging is performed for evaluating the pattern shape, is called an evaluation point, and hereinafter abbreviated as EP. The EP is designated by the user in some cases, or provided by the coordinates of a hot spot (a critical point) on the semiconductor pattern to be examined in other cases. The coordinates of the hot spot can be estimated by an exposure simulation or the like. Various dimensional values such as the wiring width of the pattern are measured based on the SEM image, and the facture of the pattern is evaluated based on these dimensional values. The result of the evaluation is fed-back to a shape correction of the mask pattern and semiconductor manufacturing process conditions, thus a high yield is realized.
In order to take an image of the EP with a small amount of imaging position misalignment and a high image quality, the following process is executed prior to the imaging of the EP. Firstly, some or all of adjustment points such as an addressing point (hereinafter referred to as AP), an automatic focus adjustment point (hereinafter referred to as AF), an automatic astigmatism adjustment point (hereinafter referred to as AST), or an automatic brightness/contrast adjustment point (hereinafter referred to as ABCC) are set if necessary. Then, addressing, an automatic focus adjustment, an automatic astigmatism adjustment, or an automatic brightness/contrast adjustment is executed at the respective adjustment points. The amount of imaging position misalignment in the addressing described above is corrected using an amount of matching difference as the amount of position misalignment of imaging. The amount of matching is obtained by matching an SEM image at the AP with known coordinates previously registered as a registered template and an SEM image (a real imaging template) observed in the actual imaging sequence with each other. The evaluation point (EP) and the adjustment points (AP, AF, AST, and ABCC) are collectively called imaging points. A position and imaging conditions of EP, and an imaging sequence and imaging conditions, an adjustment method, and the registered template of each of an imaging sequence for taking an image of the EP are managed as an imaging recipe, and the SEM executes imaging of the EP based on the imaging recipe.
When the SEM image at the EP is obtained, a desired dimension of the semiconductor pattern at a measurement point (hereinafter referred to as MP) to be measured in the EP using the SEM image.
Conventionally, the operator of the SEM manually create the recipe, and the creation of the recipe is an operation requiring energy and time. Further, since in order to register the determination of each of the adjustment points and the registered templates in the recipe, it is required to actually take an image of the wafer at low magnification, the creation of the recipe is a factor of lowering the operation rate of the SEM device. Further, as the pattern becomes miniaturized and complicated, the number of EP required to be evaluated increases explosively, and it is getting unrealistic to create the recipe manually from viewpoints of energy and creation time.
Therefore, regarding the imaging recipe, there is disclosed, in JP-A-2002-328015, a semiconductor inspection system for determining the AP based on the design data of the circuit pattern of the semiconductor described in, for example, GDSII format, further clipping the data in the AP out of the design data, and registering the data in the AP to the imaging recipe as the registered template. In this dace, since there is no need for taking an image of a real wafer only for the purpose of determination of the AP and registration of the registered template, improvement of operation rate of the SEM can be achieved. Further, the system has a function of matching, when the SEM image (a real image template) at the AP has been obtained in the actual imaging sequence, the real image template and the registered template in the design data with each other, re-registering the SEM image corresponding to the position of the registered template of the design data to the imaging recipe as the registered template, and thereafter using the registered template of the SEM image thus re-registered in the addressing processing. Further, the system has a function of automatically detecting a characteristic part of the pattern from the design data, and registering the part as the AP.
Further, JP-A-2007-250528 describes a method of creating the imaging recipe for observing the EP using CAD data. The document describes that some or all of the items including the number, coordinates, and dimensions/shapes of imaging points, an imaging sequence, a method of changing an imaging position, and imaging conditions necessary for the observation are automatically obtained from the CAD data. The document further describes that an operation of creating the image recipe is executed offline using the CAD data instead of the SEM image of a real wafer.
In other words, in the related art, the specification and the characteristics of the measurement tool (SEM) side for realizing the measurement expected by the user at the EP has not been considered. Therefore, there have arisen many cases in which correction of the recipe by the operator is required after the recipe has been created.
Further, in the related art, there has been made no consideration of sharing the recipe creation system and the information created or obtained by the system among a plurality of SEM devices, and therefore, recipe creation is required to be executed by every device. Further, there has been made no consideration of sharing the imaging/measurement data obtained from a plurality of devices.